本国际标准是为促进局域网（LAN）上计算机和终端的互连而制定的一套国际标准之一。它通过开放系统互连（OSI）参考模型与其他国际标准相关联。本国际标准描述了ISO/IEC 8802 LAN协议中逻辑链路控制（LLC）子层的功能、特点、协议和服务。LLC子层构成数据链路层中的顶层子层（见图1），是ISO/IEC 8802活动定义和支持的各种介质访问方法的共同部分。单独的国际标准分别描述了每种介质访问方法，并指出了介质访问控制（MAC）子层在每种情况下提供的附加特性和功能，以完成LAN体系结构参考模型中定义的数据链路层的功能。本国际标准描述了网络层（第3层）、MAC子层和LLC子层管理功能的LLC子层服务规范。 网络层的服务规范提供了LLC子层以及底层和子层向网络层提供的各种服务的描述，从网络层来看。MAC子层的服务规范提供了LLC子层对MAC子层所需服务的描述。这些服务的定义独立于媒体访问方法的形式和媒体本身的性质。LLC子层管理功能的服务规范提供了向LLC子层提供的管理服务的描述。以上所有服务规范均以原语的形式给出，这些原语以抽象的方式表示LLC子层和已识别服务功能（网络层、MAC子层或LLC子层管理功能）之间的信息和控制的逻辑交换。它们不指定或约束实体或接口的实现。 本国际标准描述了为局域网上任何一对数据链路层服务接入点之间的信息传输和控制而定义的对等协议程序。LLC程序独立于特定LAN中使用的介质访问方法的类型。为了满足广泛的潜在应用，包括三种类型的数据链路控制操作（见第条）。第一种类型的操作（请参阅第条）以最低的协议复杂度跨数据链路提供数据链路无连接模式服务。当更高层提供任何基本的恢复和排序服务，从而不需要在数据链路层进行复制时，这种类型的操作可能很有用。此外，在不一定要保证每个数据链路层数据单元的交付的应用中，这种类型的操作可能很有用。本国际标准以“逻辑数据链路”的形式描述了这类服务。 “第二种类型的操作（见第条）通过数据链路提供数据链路连接模式服务，与HDLC等国际标准（见ISO/IEC 13239:1997）中提供的现有数据链路控制程序相当。

This International Standard is one of a set of international standards produced to facilitate the interconnection of computers and terminals on a Local Area Network (LAN). It is related to the other international standards by the Reference Model for Open Systems Interconnection (OSI). This International Standard describes the functions, features, protocol, and services of the Logical Link Control (LLC) sublayer in the ISO/IEC 8802 LAN Protocol. The LLC sublayer constitutes the top sublayer in the data link layer (see figure 1) and is common to the various medium access methods that are defined and supported by the ISO/IEC 8802 activity. Separate International Standards describe each medium access method individually and indicate the additional features and functions that are provided by the Medium Access Control (MAC) sublayer in each case to complete the functionality of the data link layer as defined in the LAN architectural reference model. This International Standard describes the LLC sublayer service specifications to the network layer (Layer 3), to the MAC sublayer, and to the LLC sublayer management function. The service specification to the network layer provides a description of the various services that the LLC sublayer, plus underlying layers and sublayers, offer to the network layer, as viewed from the network layer. The service specification to the MAC sublayer provides a description of the services that the LLC sublayer requires of the MAC sublayer. These services are defined so as to be independent of the form of the medium access methodology, and of the nature of the medium itself. The service specification to the LLC sublayer management function provides a description of the management services that are provided to the LLC sublayer. All of the above service specifications are given in the form of primitives that represent in an abstract way the logical exchange of information and control between the LLC sublayer and the identified service function (network layer, MAC sublayer, or LLC sublayer management function). They do not specify or constrain the implementation of entities or interfaces. This International Standard provides a description of the peer-to-peer protocol procedures that are defined for the transfer of information and control between any pair of data link layer service access points on a LAN. The LLC procedures are independent of the type of medium access method used in the particular LAN. To satisfy a broad range of potential applications, three types of data link control operation are included (see clause ). The first type of operation (see clause ) provides a data-link-connectionless-mode service across a data link with minimum protocol complexity. This type of operation may be useful when higher layers provide any essential recovery and sequencing services so that these do not need replicating in the data link layer. In addition, this type of operation may prove useful in applications where it is not essential to guarantee the delivery of every data link layer data unit. This type of service is described in this International Standard in terms of "logical data links." The second type of operation (see clause) provides a data-link-connection-mode service across a data link comparable to existing data link control procedures provided in International Standards such as HDLC (see ISO/IEC 13239:1997).